JP2015197590A - image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus configured to adjust gloss of a toner image to be formed on a sheet with a high degree of freedom.SOLUTION: An image forming apparatus 1 includes: an image forming section 40 for forming a toner image on a sheet S; a heating section 80 which irradiates a surface of the sheet S with a laser beam before the image forming section 40 forms the toner image on the sheet S, to form a recess in a laser irradiation position; and a control section 100 which controls operation of the heating section 80 forming the recess, on the basis of an input image of the toner image so that gloss of the toner image formed on the sheet S by the image forming section 40 may be uniform. The gloss of the toner image formed on the sheet S can be adjusted so as to be increased as well as decreased, thereby allowing the gloss of the toner image to be adjusted with a high degree of freedom.

Description

  The present invention relates to an image forming apparatus.

  In general, an image forming apparatus (printer, copier, facsimile, etc.) using an electrophotographic process technology generates an electrostatic latent image by irradiating (exposing) a charged photoconductor with a laser beam based on image data. Form. Then, by supplying toner from the developing device to the photosensitive member (image carrier) on which the electrostatic latent image is formed, the electrostatic latent image is visualized to form a toner image. Further, the toner image is directly or indirectly transferred to a sheet, and then heated and pressed to fix it, thereby forming an image on the sheet.

  In recent years, image forming apparatuses have been required to output images with higher image quality. One of the image quality evaluation scales is the glossiness of a printed image. For example, a photographic image is required to be a glossy image, but a character image is required to be a non-glossy image for reasons such as easy reading of characters.

  In Japanese Patent Laid-Open No. 2004-260, unevenness is formed on the surface of a toner image by subjecting a paper (recording material) carrying a toner image fixed by a fixing device to fine processing (specifically, irradiation with a light beam). Thus, a glossiness adjusting device for adjusting the glossiness of the toner image has been proposed. In the technique described in Japanese Patent Application Laid-Open No. H10-228707, a photographic image area where high glossiness is desired is not subjected to glossiness adjustment processing, or weak glossiness adjustment processing is performed, while a character image region where low glossiness is desired. Is subjected to strong glossiness adjustment processing.

JP 2009-58730 A

  However, as in the technique described in Patent Document 1, the method of adjusting the glossiness of the toner image by forming irregularities on the surface of the toner image can only be adjusted in the direction of decreasing the glossiness. There was a problem that the degree of freedom was small. For example, when adjusting the gloss level so that the gloss level of the fixed toner image is uniform overall, the gloss level of the toner image must be adjusted to the lowest gloss level, and the gloss level is unnecessarily lowered. There are times when parts that end up occur. In such a case, it is not preferable to adjust the gloss level for a photographic image for which a high gloss level is desired.

  An object of the present invention is to provide an image forming apparatus capable of adjusting the glossiness of a toner image formed on a sheet with a high degree of freedom.

An image forming apparatus according to the present invention includes:
An image forming unit for forming a toner image on paper;
A heating unit that forms a recess at a heated position by heating the surface of the sheet before the toner image is formed on the sheet by the image forming unit;
Control the forming operation of the recess by the heating unit based on the input image of the toner image so that the glossiness on the paper becomes uniform after the toner image is formed on the paper by the image forming unit. A control unit,
Characterized by comprising

  According to the present invention, since the concave portion is formed on the surface of the paper so that the glossiness on the paper becomes uniform after the toner image is formed on the paper, the glossiness of the toner image formed on the paper is reduced. It is possible to adjust not only in the direction to be increased, but also in the direction in which it is increased, and the glossiness of the toner image can be adjusted with high flexibility.

1 is a diagram schematically showing an overall configuration of an image forming apparatus in the present embodiment. FIG. 2 is a diagram illustrating a main part of a control system of the image forming apparatus according to the present embodiment. It is a figure which shows the structure of the heating part in this Embodiment. It is a figure which shows the photodischarge curve (PIDC characteristic) of a photoconductor drum. It is a graph showing the relationship between the gradation level of an input image, and glossiness. 6 is a graph showing a relationship between a gradation level of an input image and a difference in glossiness (paper surface-toner image). FIG. 10 is a schematic diagram illustrating an image cross section at a position where the gradation level of an input image is 0 [%] on a highly smooth sheet. FIG. 6 is a schematic diagram illustrating an image cross section at a position where the gradation level of an input image is 50 [%] on a highly smooth sheet. FIG. 10 is a schematic diagram illustrating an image cross section at a position where the gradation level of an input image is 100 [%] on a highly smooth sheet. FIG. 10 is a schematic diagram illustrating an image cross section at a position where the gradation level of an input image is 0 [%] for a sheet with low smoothness. FIG. 10 is a schematic diagram illustrating an image cross section at a position where a gradation level of an input image is 50 [%] for a sheet having low smoothness. FIG. 6 is a schematic diagram illustrating an image cross section at a position where a gradation level of an input image is 100 [%] for a sheet with low smoothness. It is a graph showing the relationship between the gradation level of an input image, and the irradiation energy of a laser beam. 4 is a flowchart illustrating an operation example of the image forming apparatus in the present embodiment.

  Hereinafter, the present embodiment will be described in detail with reference to the drawings. FIG. 1 is a diagram schematically showing an overall configuration of an image forming apparatus 1 according to an embodiment of the present invention. FIG. 2 shows a main part of the control system of the image forming apparatus 1 according to the present embodiment. An image forming apparatus 1 shown in FIGS. 1 and 2 is an intermediate transfer type color image forming apparatus using electrophotographic process technology. In other words, the image forming apparatus 1 has each color of Y (yellow), M (magenta), C (cyan), and K (black) formed on the photosensitive drum 413 (corresponding to the “image carrier” of the present invention). The toner image is transferred (primary transfer) to the intermediate transfer belt 421, and the four color toner images are superimposed on the intermediate transfer belt 421, and then transferred to the paper S (secondary transfer), thereby forming an image. For example, when a photographic image is formed on the paper S, since it is required to be a glossy image, the paper S (for example, coated paper) having a high surface smoothness is used. Further, when a character image is formed on the paper S, it is required to be a non-glossy image for reasons such as easy reading of the characters, and thus paper S (for example, mat paper) with low surface smoothness is used. .

  Further, in the image forming apparatus 1, the photosensitive drums 413 corresponding to the four colors of YMCK are arranged in series in the running direction of the intermediate transfer belt 421, and the respective color toner images are sequentially transferred to the intermediate transfer belt 421 in one procedure. Tandem system is adopted.

  As shown in FIG. 2, the image forming apparatus 1 includes an image reading unit 10, an operation display unit 20, an image processing unit 30, an image forming unit 40, a paper transport unit 50, a fixing unit 60, a heating unit 80, and a control unit 100. Prepare.

  The control unit 100 includes a CPU (Central Processing Unit) 101, a ROM (Read Only Memory) 102, a RAM (Random Access Memory) 103, and the like. The CPU 101 reads a program corresponding to the processing content from the ROM 102 and develops it in the RAM 103, and centrally controls the operation of each block of the image forming apparatus 1 in cooperation with the developed program. At this time, various data stored in the storage unit 72 is referred to. The storage unit 72 includes, for example, a nonvolatile semiconductor memory (so-called flash memory) or a hard disk drive.

  The control unit 100 transmits and receives various data to and from an external device (for example, a personal computer) connected to a communication network such as a LAN (Local Area Network) or a WAN (Wide Area Network) via the communication unit 71. Do. For example, the control unit 100 receives image data transmitted from an external device, and forms an image on the paper S based on the image data (input image data). The communication unit 71 is composed of a communication control card such as a LAN card, for example.

  The image reading unit 10 includes an automatic document feeder 11 called an ADF (Auto Document Feeder), a document image scanning device 12 (scanner), and the like.

  The automatic document feeder 11 transports the document D placed on the document tray by a transport mechanism and sends it out to the document image scanning device 12. The automatic document feeder 11 can continuously read images (including both sides) of a large number of documents D placed on a document tray all at once.

  The document image scanning device 12 optically scans a document conveyed on the contact glass from the automatic document feeder 11 or a document placed on the contact glass, and reflects light from the document to a CCD (Charge Coupled Device). ) An image is formed on the light receiving surface of the sensor 12a, and an original image is read. The image reading unit 10 generates input image data based on the reading result by the document image scanning device 12. The input image data is subjected to predetermined image processing in the image processing unit 30.

  The operation display unit 20 is configured by, for example, a liquid crystal display (LCD) with a touch panel, and functions as a display unit 21 and an operation unit 22. The display unit 21 displays various operation screens, an image status display, an operation status of each function, and the like in accordance with a display control signal input from the control unit 100. The operation unit 22 includes various operation keys such as a numeric keypad and a start key, receives various input operations by the user, and outputs an operation signal to the control unit 100.

  The image processing unit 30 includes a circuit that performs digital image processing on input image data according to initial settings or user settings. For example, the image processing unit 30 performs gradation correction based on the gradation correction data (gradation correction table) under the control of the control unit 100. Further, the image processing unit 30 performs various correction processes such as color correction and shading correction, a compression process, and the like on the input image data in addition to the gradation correction. The image forming unit 40 is controlled based on the image data subjected to these processes.

  The image forming unit 40 is based on the input image data, and image forming units 41Y, 41M, 41C, 41K, and an intermediate transfer unit 42 for forming an image using colored toners of Y component, M component, C component, and K component. Etc.

  The Y component, M component, C component, and K component image forming units 41Y, 41M, 41C, and 41K have the same configuration. For convenience of illustration and explanation, common constituent elements are denoted by the same reference numerals, and Y, M, C, or K are added to the reference numerals when distinguished from each other. In FIG. 1, only the components of the Y-component image forming unit 41Y are denoted by reference numerals, and the constituent elements of the other image forming units 41M, 41C, and 41K are omitted.

  The image forming unit 41 includes an exposure device 411, a developing device 412, a photosensitive drum 413, a charging device 414, a drum cleaning device 415, and the like.

  The photosensitive drum 413 has an undercoat layer (UCL) and a charge generation layer (CGL) on the peripheral surface of an aluminum conductive cylinder (aluminum tube) having a drum diameter of 80 mm, for example. It is a negatively charged organic photoconductor (OPC) in which a generation layer (CTL) and a charge transport layer (CTL) are sequentially stacked. The charge generation layer is made of an organic semiconductor in which a charge generation material (for example, phthalocyanine pigment) is dispersed in a resin binder (for example, polycarbonate), and generates a pair of positive charges and negative charges by exposure by the exposure device 411. The charge transport layer consists of a material in which a hole transport material (electron donating nitrogen-containing compound) is dispersed in a resin binder (for example, polycarbonate resin), and transports positive charges generated in the charge generation layer to the surface of the charge transport layer. To do.

  The control unit 100 controls a drive current supplied to a drive motor (not shown) that rotates the photosensitive drum 413, so that the photosensitive drum 413 rotates at a constant peripheral speed.

  The charging device 414 uniformly charges the surface of the photoconductive drum 413 to a negative polarity. The exposure device 411 is composed of, for example, a semiconductor laser, and irradiates the photosensitive drum 413 with laser light corresponding to the image of each color component. A positive charge is generated in the charge generation layer of the photosensitive drum 413 and is transported to the surface of the charge transport layer, whereby the surface charge (negative charge) of the photosensitive drum 413 is neutralized. An electrostatic latent image of each color component is formed on the surface of the photosensitive drum 413 due to a potential difference from the surroundings.

  The developing device 412 is, for example, a two-component developing type developing device, and forms a toner image by visualizing the electrostatic latent image by attaching toner of each color component to the surface of the photosensitive drum 413.

  The drum cleaning device 415 includes a drum cleaning blade that is slidably contacted with the surface of the photosensitive drum 413, and removes transfer residual toner remaining on the surface of the photosensitive drum 413 after primary transfer.

  The intermediate transfer unit 42 includes an intermediate transfer belt 421, a primary transfer roller 422, a plurality of support rollers 423, a secondary transfer roller 424, a belt cleaning device 426, and the like.

  The intermediate transfer belt 421 is an endless belt, and is stretched around a plurality of support rollers 423 in a loop shape. At least one of the plurality of support rollers 423 is configured by a driving roller, and the other is configured by a driven roller. For example, it is preferable that the roller 423A disposed downstream of the K component primary transfer roller 422 in the belt traveling direction is a drive roller. This makes it easy to keep the belt running speed constant in the primary transfer portion. As the driving roller 423A rotates, the intermediate transfer belt 421 travels in the direction of arrow A at a constant speed.

  The primary transfer roller 422 is disposed on the inner peripheral surface side of the intermediate transfer belt 421 so as to face the photosensitive drum 413 of each color component. The primary transfer roller 422 is pressed against the photosensitive drum 413 with the intermediate transfer belt 421 interposed therebetween, whereby a primary transfer nip for transferring a toner image from the photosensitive drum 413 to the intermediate transfer belt 421 is formed.

  The secondary transfer roller 424 is disposed on the outer peripheral surface side of the intermediate transfer belt 421 so as to face a roller 423B (hereinafter referred to as “backup roller 423B”) disposed on the downstream side of the driving roller 423A in the belt traveling direction. The secondary transfer roller 424 is pressed against the backup roller 423B with the intermediate transfer belt 421 interposed therebetween, thereby forming a secondary transfer nip for transferring the toner image from the intermediate transfer belt 421 to the sheet S.

  When the intermediate transfer belt 421 passes through the primary transfer nip, the toner images on the photoconductive drum 413 are primarily transferred onto the intermediate transfer belt 421 in sequence. Specifically, by applying a primary transfer bias to the primary transfer roller 422 and applying a charge having a polarity opposite to that of the toner to the back side of the intermediate transfer belt 421 (the side in contact with the primary transfer roller 422), the toner image becomes It is electrostatically transferred to the intermediate transfer belt 421.

  Thereafter, when the sheet S passes through the secondary transfer nip, the toner image on the intermediate transfer belt 421 is secondarily transferred to the sheet S. Specifically, a toner image is applied by applying a secondary transfer bias to the secondary transfer roller 424 and applying a charge having a polarity opposite to that of the toner to the back side of the paper S (the side in contact with the secondary transfer roller 424). Is electrostatically transferred to the paper S. The sheet S on which the toner image has been transferred is conveyed toward the fixing unit 60.

  The belt cleaning unit 426 includes a belt cleaning blade that is in sliding contact with the surface of the intermediate transfer belt 421 and removes transfer residual toner remaining on the surface of the intermediate transfer belt 421 after the secondary transfer. Instead of the secondary transfer roller 424, a configuration (so-called belt-type secondary transfer unit) in which a secondary transfer belt is looped around a plurality of support rollers including the secondary transfer roller is adopted. Also good.

  The fixing unit 60 includes an upper fixing unit 60A having a fixing surface side member disposed on the fixing surface (surface on which the toner image is formed) of the paper S, and a back surface (surface opposite to the fixing surface) of the paper S. A lower fixing unit 60B having a rear side support member to be disposed, a heating source 60C, and the like are provided. When the back surface side support member is pressed against the fixing surface side member, a fixing nip for nipping and transporting the paper S is formed.

  The fixing unit 60 fixes the toner image on the paper S by heating and pressurizing the paper S on which the toner image has been secondarily transferred and conveyed at the fixing nip part. The fixing unit 60 is disposed in the fixing device F as a unit. The fixing device F may be provided with an air separation unit that separates the sheet S from the fixing surface side member or the back surface side support member by blowing air.

  The paper transport unit 50 includes a paper feed unit 51, a paper discharge unit 52, a transport path unit 53, and the like. In the three paper feed tray units 51a to 51c constituting the paper feed unit 51, paper S (standard paper, special paper) identified based on basis weight, size, etc. is stored for each preset type. . The conveyance path unit 53 includes a plurality of conveyance roller pairs such as registration roller pairs 53a.

  The sheets S stored in the sheet feed tray units 51 a to 51 c are sent one by one from the top and are conveyed to the image forming unit 40 by the conveyance path unit 53. At this time, the registration roller portion provided with the registration roller pair 53a corrects the inclination of the fed paper S and adjusts the conveyance timing. That is, at the timing when the leading edge of the toner image on the surface of the photosensitive drum 413 is conveyed to the secondary transfer nip, the registration roller pair 53a is set so that the printing start position of the sheet S coincides with the secondary transfer nip. The rotation is started and the sheet S is conveyed to the secondary transfer nip. In the image forming unit 40, the toner image on the intermediate transfer belt 421 is secondarily transferred to one side of the sheet S at a time, and the fixing unit 60 performs a fixing process. The sheet S on which the fixing process has been performed is discharged out of the apparatus by a paper discharge unit 52 having a paper discharge roller 52a.

The heating unit 80 is downstream of the registration roller pair 53a in the conveyance direction (arrow C direction) of the sheet S and upstream of the secondary transfer nip NP for transferring the toner image from the intermediate transfer belt 421 to the sheet S. Has been placed. The heating unit 80 heats the surface of the sheet S by irradiating the surface of the sheet S with a laser beam at the position B on the sheet conveyance path 90, and forms a recess at the heated position. The concave portion is a portion where a part of the paper S is removed by thermal decomposition or combustion by applying thermal energy when irradiated with laser light. The depth of the recess formed on the surface of the paper S can be adjusted by changing the irradiation energy (irradiation intensity) [W / mm ² ] of the laser beam. As a method for changing the irradiation energy, for example, there are a method for adjusting the emission intensity of laser light, a method for adjusting the irradiation time (light emission time) of laser light, and the like.

  The heating unit 80 uses a part of the laser light for performing exposure processing on the photosensitive drum 413 as the laser light with which the surface of the paper S is irradiated. As shown in FIG. 3, the laser beam 110 irradiated from the exposure device 411 included in the K-component image forming unit 41K is transmitted through the branched laser beam 110a that travels to the surface of the photosensitive drum 413, and is reflected and heated. A mirror 411 a for branching to the branched laser beam 110 b that proceeds to the unit 80 is provided on the optical path of the laser beam 110. The heating unit 80 takes in the branched laser beam 110b and irradiates the surface of the paper S with the laser beam using the branched laser beam 110b. By configuring the heating unit 80 in this way, it is possible to avoid an increase in cost due to the addition of a dedicated laser light irradiation device that irradiates the surface of the paper S with laser light.

  In this embodiment, since the laser beam 110 irradiated from the exposure device 411 is branched into the branched laser beam 110a and the branched laser beam 110b, the amount of laser beam irradiated to the photosensitive drum 413 is reduced, There is a possibility that the exposure process for the photosensitive drum 413 may be hindered. Therefore, the control unit 100 sets the minimum light amount of the laser light 110 emitted from the exposure apparatus 411 as follows.

  FIG. 4 shows a photodischarge curve (PIDC characteristic) of the photosensitive drum 413. The PIDC characteristic indicates the relationship between the surface potential of the photosensitive drum 413 and the irradiation energy (exposure energy) of laser light. As shown in FIG. 4, the surface potential of the photosensitive drum 413 charged to a predetermined potential (for example, −600 [V]) by the charging device 414 becomes zero as the value of the irradiation energy received by the laser light irradiation increases. Attenuates near [V]. If the value of irradiation energy is large enough to enter the potential saturation region of PIDC characteristics (region where the rate of change of the surface potential of the photosensitive drum 413 with respect to the change of irradiation energy is sufficiently small), the photosensitive member can be changed even if the irradiation energy is changed. The surface potential of the drum 413 is substantially constant. The controller 100 irradiates the photosensitive drum 413 with the laser light even if the amount of the laser light for performing the exposure process decreases due to the branching of the laser light 110 emitted from the exposure device 411. The minimum light amount of the laser beam 110 irradiated from the exposure device 411 is set so that the energy enters the potential saturation region. As a result, it is possible to avoid the possibility that the exposure process with respect to the photosensitive drum 413 is hindered, and as a result, it is possible to ensure the quality of the toner image formed on the paper S.

In addition to the K component image forming unit 41K, the heating unit 80 applies the laser light 110 emitted from the exposure device 411 included in the Y, M, and C component image forming units 41Y, 41M, and 41C. You may utilize as a laser beam irradiated with respect to the surface of the paper S. FIG. Further, the heating unit 80 does not necessarily use part of the laser light for performing the exposure process on the photosensitive drum 413. In this case, the heating unit 80 includes a light source that generates laser light for forming a recess in the paper S. As the light source, for example, a laser oscillation device such as a YAG laser (Yttrium, Aluminum, Garnet laser, emission wavelength: 1.064 [μm]) or a CO ₂ laser (emission wavelength: 10.6 [μm]) can be used. .

  In the laser beam irradiation process on the surface of the paper S, the glossiness of the toner image changes according to the change in the gradation level of the toner image (input image) formed on the paper S, and as a result, the gloss on the paper S This is done to cope with the problem that the degree of unevenness and gloss unevenness occur. In the electrophotographic image forming apparatus 1, the gradation representation of each color toner image of Y (yellow), M (magenta), C (cyan), and K (black) is represented by area gradation (screen, halftone dot). This is because the surface of the toner image is uneven on a microscopic scale, and the toner adhesion amount and the toner height formed on the paper S change according to the gradation level. Here, as the toner adhesion amount increases (the toner height increases), the amount of light transmitted to the inside decreases and the regular reflection component increases, so that the glossiness increases.

  FIG. 5 is a graph showing the correspondence (gradation-glossiness characteristic) between the gradation level [%] of the input image and the glossiness of the toner image formed on the paper S corresponding to the input image. In the example shown in FIG. 5, the gradation-gloss characteristics differ for each type of paper S (plain paper, coated paper). In the present embodiment, characteristic information representing gradation-glossiness characteristics as an approximate expression or a table value is set for each type of paper S (plain paper, coated paper) and stored in the storage unit 72. Note that although the tone-gloss characteristics are slightly different for each of Y, M, C, and K colors, all colors have characteristics as shown in FIG.

  FIG. 6 shows the correspondence between the gradation level [%] of the input image and the difference in glossiness obtained by subtracting the glossiness of the surface of the paper S from the glossiness of the toner image formed on the paper S corresponding to the input image. The graph showing a relationship is shown. As shown in FIG. 6, the glossiness on the paper S is non-uniform according to the change in the gradation level of the input image.

  Next, a mechanism for changing the glossiness of the toner image formed on the paper S in accordance with the change in the gradation level of the input image will be described. When the paper S is a coated paper, in an area where the gradation level of the input image is 0 [%], no toner is placed on the paper S as shown in FIG. Therefore, the glossiness in the region where the gradation level is 0 [%] depends on the surface property of the paper S. The surface of the paper S (coated paper) has high smoothness. Therefore, as shown in FIG. 5, the glossiness in a region where the gradation level is 0 [%] shows a high numerical value.

  When the gradation level of the input image increases, irregularities (steps) due to the toner image I occur on the paper S as shown in FIG. 8A (gradation level: 50 [%]). Because of this step, the specular reflection light decreases and the irregular reflection light increases, so that the glossiness becomes smaller than the region where the gradation level is 0% as shown in FIG. As shown in FIG. 6, the glossiness in the region where the gradation level is 40 [%] is the smallest.

  Thereafter, as the gradation level increases, the amount of toner on the surface of the paper S increases, and the surface of the toner image gradually becomes smoother. When the gradation level reaches 100 [%], as shown in FIG. 9A, a predetermined amount (predetermined height) of toner is uniformly placed on the paper S. Since the surface of the toner image having a uniform toner height has high smoothness, the glossiness is larger than the area where the gradation level is 0% as shown in FIG.

  On the other hand, when the paper S is plain paper, in a region where the gradation level of the toner image is 0 [%], no toner is placed on the paper S as shown in FIG. Therefore, the glossiness in the region where the gradation level is 0 [%] depends on the surface property of the paper S. The surface of the paper S (plain paper) has irregularities (steps), and the smoothness of the surface is low. This step reduces regular reflection light and increases irregular reflection light. Therefore, as shown in FIG. 5, the glossiness in the region where the gradation level is 0 [%] is lower than that in the case where the paper S is coated paper.

  When the gradation level of the input image increases, as shown in FIG. 11 (gradation level: 50 [%]), the toner image I enters (fills) the concave portion existing on the surface of the paper S, and the level difference on the paper S Decrease. However, the situation in which the specular reflection light decreases and the irregular reflection light increases does not change due to this level difference, so the glossiness is equivalent to the region where the gradation level is 0 [%] as shown in FIG.

  Thereafter, as the gradation level increases, the amount of toner occupying the surface of the sheet S increases, and when the gradation level reaches 100%, the entire surface of the sheet S (recesses and protrusions) as shown in FIG. 12A. ) Is in a state where toner is loaded. Therefore, as shown in FIG. 5, the glossiness on the paper S is larger than the area where the gradation levels are 0 [%] and 50 [%]. However, a step is generated between the toner placed on the concave portion of the paper S and the toner placed on the convex portion of the paper S, and the regular reflection light is reduced and the irregular reflection light is increased by the step. Therefore, as shown in FIG. 5, the glossiness in the region where the gradation level is 100 [%] is smaller than when the paper S is coated paper.

  In the present embodiment, the control unit 100 uses the characteristic information stored in the storage unit 72 to prevent gloss unevenness from occurring on the paper S after the toner image is formed based on the input image. As shown, the gloss level on the paper S after the toner image is formed becomes uniform even when the gradation level of the input image changes (more specifically, the gradation level is 0 [%]). The concave portion forming operation by the heating unit 80 is controlled so as to be equivalent to the glossiness of a certain region.

  For example, when the paper S is coated paper, the gloss level of the input image has a gradation level of 50 [%] (that is, the glossiness of the toner image is smaller than the glossiness of the region having a gradation level of 0 [%]). In the region, the control unit 100 controls the heating unit 80 to irradiate the laser light (arrow) onto the position where the toner I is placed on the surface of the paper S, thereby forming a recess (FIG. 8B). See). The depth of the recess is, for example, the same as the toner height L1 (constant) of the toner I. As a result, when a toner image is formed on the paper S, the toner I enters a concave portion formed by laser light irradiation, and the concave and convex portions (steps) on the surface of the paper S do not form a concave portion (see FIG. 8A). (See FIG. 8C). That is, the glossiness of the toner image increases so as to approach the glossiness of the region where the gradation level is 0 [%]. Note that the depth of the concave portion to be formed may be changed larger or smaller than L1. By arbitrarily changing the depth of the recess, the amount of increase in the glossiness on the paper S can be arbitrarily controlled.

  Further, when the paper S is coated paper, the toner image has a gradation level of 100 [%] (that is, the glossiness of the toner image is larger than the glossiness when the gradation level is 0 [%]). In the region, the control unit 100 controls the heating unit 80 to irradiate the surface of the paper S with laser light (arrows) at regular intervals, thereby forming recesses at regular intervals (FIG. 9B). See). The depth of the recess is, for example, L2 larger than the toner height L1 of the toner I. As a result, when the toner image is formed on the paper S, unlike the case where the concave portion is not formed (see FIG. 9A), the toner I is placed on the entire surface (the concave portion and the convex portion) of the paper S. A step is generated between the toner I placed on the concave portion of the toner and the toner I placed on the convex portion of the paper S, and the regular reflected light is reduced and the irregularly reflected light is increased by the step (see FIG. 9C). . That is, the glossiness on the paper S decreases so as to approach the glossiness of the region where the gradation level is 0 [%]. Note that the depth of the concave portion to be formed may be changed larger or smaller than L2. The amount of decrease in the glossiness on the paper S can be arbitrarily controlled by arbitrarily changing the depth of the recess.

  When the paper S is plain paper, the input image has a gradation level of 100 [%] (that is, the glossiness of the toner image is greater than the glossiness when the gradation level is 0 [%]). In the region), the control unit 100 controls the heating unit 80 to increase the depth of the recess by irradiating the position of the recess existing on the paper S with a laser beam (arrow) (see FIG. 12B). The increased depth of the concave portion is, for example, L3 larger than the toner height of the toner I. As a result, when the toner image is formed on the paper S, the toner I placed on the concave portion of the paper S and the convex portion of the paper S are compared with the case where the depth of the concave portion is not increased (see FIG. 12A). The difference in level between the toner I and the toner I is increased (see FIG. 12C). That is, the glossiness on the paper S decreases so as to approach the glossiness of the region where the gradation level is 0 [%]. Note that the depth of the concave portion to be formed may be changed larger or smaller than L3. The amount of decrease in the glossiness on the paper S can be arbitrarily controlled by arbitrarily changing the depth of the recess.

  FIG. 13 is a graph showing a correspondence relationship between the gradation level of the input image and the irradiation energy of the laser light irradiated by the heating unit 80 for each type of paper S (plain paper, coated paper). The storage unit 72 may store second characteristic information in which the correspondence relationship between the gradation level of the input image and the irradiation energy of the laser light is expressed by an approximate expression or a table value. In this case, the control unit 100 refers to the second characteristic information stored in the storage unit 72, and the glossiness on the paper S after the toner image is formed even if the gradation level of the input image changes. The laser beam irradiation energy is changed in accordance with the change in the gradation level so as to be uniform.

  Next, the operation of the image forming apparatus 1 in the present embodiment will be described with reference to the flowchart of FIG. Note that the processing shown in FIG. 14 is executed, for example, at the timing of executing the image forming processing corresponding to the print job.

  First, the control unit 100 acquires input image data corresponding to a print job from the image processing unit 30 (step S100). Next, the control unit 100 acquires paper information corresponding to the print job from the storage unit 72 (step S120). Next, the control unit 100 acquires characteristic information corresponding to the sheet S indicated by the acquired sheet information from the storage unit 72 (step S140).

  Next, the control unit 100 determines whether the smoothness of the paper S indicated by the paper information is high or low (step S160). As a result of this determination, when the smoothness of the paper S is high (step S160, YES), the control unit 100 determines the position where the concave portion is formed on the surface of the paper S (step S180: first determination process). Specifically, the control unit 100 determines that the glossiness of the toner image is smaller than the glossiness of the region (the surface of the paper S) where the gradation level is 0 [%]. It is determined that the concave portion is formed by irradiating the surface where the toner I is placed with the laser beam. Further, the control unit 100 controls the surface of the paper S in a region where the glossiness of the toner image is larger than the glossiness of the region (the surface of the paper S) where the gradation level is 0%. Then, it is determined that the concave portions are formed at regular intervals by irradiating laser light at regular intervals.

  On the other hand, when the smoothness of the paper S is low (step S160, NO), the control unit 100 determines the position where the concave portion is formed on the surface of the paper S (step S200: second determination process). Specifically, the control unit 100 determines that the glossiness of the toner image is larger than the glossiness of the region (surface of the paper S) where the gradation level is 0 [%]. It is determined that the depth of the concave portion is increased by irradiating the position of the concave portion existing in the laser beam with laser light.

  Lastly, the control unit 100 controls the concave portion forming operation by the heating unit 80 based on the determination in step S180 or S200 at the timing when the sheet S passes through the position B on the sheet conveyance path 90 (step S220). ). When the process of step S220 is completed, the image forming apparatus 1 ends the process in FIG.

  As described above in detail, in the present embodiment, the image forming apparatus 1 includes the image forming unit 40 that forms a toner image on the paper S, and the paper before the toner image is formed on the paper S by the image forming unit 40. By irradiating the surface of S with a laser beam, a heating unit 80 that forms a recess at a position irradiated with the laser beam, and on the sheet S after the toner image is formed on the sheet S by the image forming unit 40 And a control unit 100 for controlling the concave portion forming operation by the heating unit 80 based on the input image of the toner image so that the glossiness of the toner image becomes uniform.

  According to the present embodiment configured as described above, the concave portion is formed on the surface of the paper S so that the glossiness on the paper S after the toner image is formed on the paper S is uniform. The toner image formed on the toner image can be adjusted not only in the direction of decreasing the glossiness but also in the increasing direction, and the glossiness of the toner image can be adjusted with a high degree of freedom.

  In the above embodiment, the heating unit 80 has been described with respect to the example in which the concave portion is formed by irradiating the surface of the paper S with laser light. However, the present invention is not limited to this. For example, a thermal head that has a plurality of heating elements arranged in the paper width direction orthogonal to the transport direction of the paper S and forms a recess by heating the surface of the paper S may be adopted as the heating unit 80. good.

  In addition, each of the above-described embodiments is merely an example of actualization in carrying out the present invention, and the technical scope of the present invention should not be construed in a limited manner. That is, the present invention can be implemented in various forms without departing from the gist or the main features thereof.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 10 Image reading part 20 Operation display part 21 Display part 22 Operation part 30 Image processing part 40 Image forming part 50 Paper conveyance part 60 Fixing part 71 Communication part 72 Storage part 80 Heating part 100 Control part 101 CPU
102 ROM
103 RAM
413 Photosensitive drum

Claims (7)

An image forming unit for forming a toner image on paper;
A heating unit that forms a recess at a heated position by heating the surface of the sheet before the toner image is formed on the sheet by the image forming unit;
Control the forming operation of the recess by the heating unit based on the input image of the toner image so that the glossiness on the paper becomes uniform after the toner image is formed on the paper by the image forming unit. A control unit,
An image forming apparatus comprising:   The image forming apparatus according to claim 1, wherein the heating unit forms the concave portion by irradiating a surface of the paper with a laser beam.   The image forming apparatus according to claim 2, wherein the heating unit uses a laser beam for performing an exposure process on the image carrier as a laser beam applied to the surface of the paper.   The control unit is configured to select, based on a correspondence relationship between a gradation level of the input image and a gloss level of the toner image formed on the paper corresponding to the input image, among the toner images formed on the paper. The image forming apparatus according to claim 1, wherein a gradation level that is a target for forming the concave portion is determined.   The image forming apparatus according to claim 4, wherein the control unit determines a position where the concave portion is to be formed in a gradation level region to be the target of forming the concave portion.   The image forming apparatus according to claim 4, wherein the control unit determines a position where the concave portion is to be formed and a depth of the concave portion in a gradation level region which is a target for forming the concave portion. .   The image forming apparatus according to claim 4, wherein the correspondence relationship is set for each type of the sheet.

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